This invention relates to equipment used for producing wells.
Oil and gas wells have been produced by a jet pump in which inner and outer strings of tubing are connected downhole using a venturi, and liquid flow through the outer tubing string then through the venturi into the inner tubing string draws production fluid into the inner tubing through an opening into the inner tubing. This process has been found to work, but requires a suitable liquid.
Cleaning out wells conventionally with a coiled tubing unit is accomplished by forcing compressed air/gas down the coiled tubing to the bottom of the well and returning the fluid/fill up the annulus between the coiled tubing and the wells original production casing. The fluids are carried up the annulus in slugs causing a pressure build-up in the lower portion of the well. This pressure build up may force fluids, fill, and air back into the producing zone, which may cause formation damage. Wells with production casing larger than four and one half inch are difficult to clean out due to reduced annular velocity of the compressed air. To clean a well out in this manner, the casing gas is vented to atmosphere through the entire job. This is expensive and not environmentally friendly. This invention is directed to providing an improved pumping system.
There is therefore provided in accordance with the invention a wellsite pumping system, comprising a gas processing system including a source of compressed gas, the source of compressed gas having a low pressure inlet and a high pressure outlet, coil tubing connected to the high pressure outlet of the gas processing system, the coil tubing including a first tubing string connected to the high pressure outlet and a second tubing string running parallel to the first tubing string and having an opening for entry of fluid at a remote end from the high pressure outlet; and a venturi connecting the second tubing string to the first tubing string such that, in operation, passage of gas through the venturi from the first tubing string draws production fluid into the second tubing string. Preferably, the second tubing string is suspended within the first tubing string. The venturi may be formed by a horizontal passageway communicating with a vertical passageway with a restriction.
In one aspect of the invention, the source of compressed gas forms part of a wellsite inert gas injector. The inert gas injector comprises an internal combustion engine, a gas processing system connected to receive low pressure exhaust gas from the internal combustion engine, a pump within the gas processing system, the pump having a low pressure inlet for receiving exhaust gases and the pump having a high pressure outlet; and coil tubing connected to the high pressure outlet of the gas processing system. The gas processing system preferably comprises one or more of a particulate filter, exhaust cooler and exhaust separator in series, and in that order before the pump. The pump may be a compressor.